Growth of sweetpotato cultured in the newly designed
hydroponic system for space farming
Life support of crews in long-duration space missions for other planets will be highly dependent on amounts of food, atmospheric
O2 and clean water produced by plants. Therefore, the space farming system with scheduling of crop production, obtaining
high yields with a rapid turnover rate, converting atmospheric CO2 to O2 and purifying water should be established with employing
suitable plant species and cultivars and precisely controlling environmental variables around plants grown at a high density in a
limited space. In this study, we developed a new hydroponic method for producing tuberous roots and fresh edible leaves and stems
of sweetpotato. In the first experiment, we examined the effects of water contents in the rooting substrate on growth and tuberous
root development of sweetpotato. The rooting substrates made with rockwool slabs were inclined in a culture container and
absorbed nutrient solution from the lower end of the slabs by capillary action. Tuberous roots developed on the lower surface
of the rockwool slabs. The tuberous roots showed better growth and development at locations farther from the water surface
on the rockwool slabs, which had lower water content. In the second experiment, three sweetpotato cultivars were cultured in a
hydroponic system for five months from June to November under the sun light in Osaka, Japan as a fundamental study for establishing
the space farming system. The cultivars employed were ‘Elegant summer’, ‘Kokei-14’ and ‘Beniazuma’. The hydroponic system
mainly consisted of culture containers and rockwool slabs. Dry weights of tuberous roots developed in the aerial space between
the rockwool slab and the nutrient solution filled at the bottom of the culture container were 0.34, 0.45 and 0.23 kg/plant and dry
weights of the top portion (leaves, petioles and stems) were 0.42, 0.29 and 0.61 kg/plant for ‘Elegant summer’, ‘Kokei-14’ and ‘Beniazuma’,
respectively. Young stems and leaves as well as tuberous roots of ‘Elegant summer’ are edible and palatable. Therefore
‘Elegant summer’ would be a promising crop to produce large amounts of food with high nutritional values in the present hydroponic
system in space farming.